2001 AES Annual Meeting Abstracts

The oldest undoubted lamniform sharks are known from the Aptian of Texas. These consist of teeth that although small, show all of the charactistics and tooth positions of the genusCarcharias. Because of this,it is maintained that Carcharias is the most primitive lamniform genus,rather than Mitsukurina as currently thought.The orectolobid suite contention that precludes an ancestral relationship to the lamniform sharks is challenged. The taxonomic position of the Jurassic Palaeocarcharias is discussed, and it is suggested that this transitional genus warrents the ordinal rank of Palaeocarchariformes. Reasons for this placement are given. The dentitions,endocrania,fins and vertebrae ofOrectobus,Palaeocarcharias,Carcharias, Scapanorhynchus and Mitsukurina are shown and there relationships considered. Some ideas are also given on ecological and behavioral changes. (Session 10, Saturday, July 7, Penn Stater, Room 207, 2:30)

Using GIS and VHF radio telemetry to evaluate shark ecology and movements in Louisiana

Little data exist for sharks in Louisiana’s coastal waters. The Coastal Fisheries Institute is conducting a three-year study to quantify the existence of shark nursery grounds in Louisiana. Experimental gillnets were used in Timbalier Bay and to date, eight species representing two families, have been observed. A Geographic Information System (GIS) was designed to investigate spatial relationships present within individual shark species and species assemblages. A shift in spatial distribution of blacktip, Carcharhinus limbatus, and Atlantic sharpnose, Rhizoprionodon terraenovae, sharks was observed. Bonnethead,Sphyrna tiburo, and scalloped hammerhead, Sphyrna lewini, sharks were only observed in the 2000 samples. A pilot study using VHF radio telemetry is currently being conducted to investigate bull shark, Carcharhinus leucas, movements in the Atchafalaya Basin. Six VHF radio transmitters were embedded in foam float tags and attached to juvenile sharks approximately one meter in length. Tagged individuals were relocated every five days and movements monitored for 24-48 hours. Telemetry data are being interpolated and analyzed in a GIS environment. GIS can be a powerful tool for examining spatial and temporal patterns in biological data, provided that the technology is utilized within the context of the biological system being examined. (Session 10, Saturday, July 7, Penn Stater, Room 207, 11:15)

Jumping sharks, with special emphasis on the blacktip shark, (Carcharhinus limbatus) 

A lot of attention has lately been given on breaching white sharks, (Carcharodon carcharias), using decoys to trigger such reactions. The motivational reason for these animals seem clear, nevertheless detailed experiments have to be conducted to understand this behavior completely. Other sharks species jump as well but for different motivational reasons. One of the most spectacular jumpers in the Caribbean and Bahamian waters is the blacktip shark, (Carcharhinus limbatus). For the first time, some of these jumps and starts have been filmed underwater making it possible to investigate this behavior from a new point of view. This paper gives an overview of why sharks jump, with special emphasis on the blacktip shark and its motivational reason. (Session 7, Saturday, July 7, Penn Stater, Room 207, 8:15)

Bycatch data for the southeastern United States commercial shark fishery

From 1994 to 2000, at-sea observers from the Florida Museum of Natural History Commercial Shark Fishery Observer Program (CSFOP) monitored and collected data on 785 longline sets, totaling 6.7 million hook hours observed. Utilizing at-sea data, we are able to quantify bycatch composition and bycatch disposition, and fishing effort. This information is unobtainable in dockside observer programs. Bycatch was allocated into six broad categories (marine mammal, sea turtle, fish, invertebrate, alga, human refuse). Fish and turtle catches were identified to species level, invertebrate catch to lowest taxonomic level. Total bycatch and catch per unit of fishing effort (CPUE) for all bycatch (2543 individuals, 3.78 individuals per 10,000 hook hrs) was significantly lower than that for targeted sharks (35554, 53.1 sharks per 10,000 hook hrs). The Florida Gulf Coast region had the highest total bycatch of all sample areas (60% of total bycatch) and highest CPUE (2.27 per 10,000 hook-hrs). There was no significant variation from year to year in total bycatch or bycatch composition. Fish dominated total bycatch composition (67.8% of total bycatch) and bycatch CPUE (2.57 per 10,000 hook-hrs) followed by invertebrates (28.4%, 1.08 per 10,000 hook-hrs). Perciform and batoid fishes comprised 87% of the total fish bycatch. The Florida Gulf coast region had the greatest diversity of fishes and invertebrates. Disposition of bycatch varied with type and commercial value. Commercially valuable fish bycatch was dominated by serranids (Epinephelus morio and Mycteroperca microlepis) encompassing 43% of the total fish bycatch, Rachycentron canadum (7%), and lutjanids (Lutjanus analis and Lutjanus buccanella, 6%). Of these commercially valuable fishes, greater than 40% were retained for sale. 57% of Sphyraena barracuda and anguilliform fishes (8% and 9% of total fish bycatch, respectively) caught were utilized as bait. Echinoids and asteroids dominated the invertebrate bycatch (44% of invertebrate bycatch). Greater than 90% of invertebrates caught as bycatch were discarded. Species of special conservation interest (sea turtles, dolphins, and seabirds) comprised less than 1% of the total bycatch (34 sea turtles, 1 dolphin, and 1 pelican). Of the 34 sea turtles caught (24 Caretta carreta, 3 Dermochelys coriacea, and 7 unidentified), 18 were released alive and 7 discarded dead. Nine turtles were released at the vessel without knowledge of condition. The single dolphin was released alive and the pelican, discarded dead. Total bycatch numbers are low when compared to the target species (sharks) catch, making this a relatively clean fishery. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Overview of the Commercial Shark Fishery Observer Program (CSFOP)

The Commercial Shark Fishery Observer Program (CSFOP) is a cooperative effort of the Florida Museum of Natural History and the fishers of the United States Atlantic commercial shark fishery. Historically supported by grants from U.S. Department of Commerce funding programs, the CSFOP places fishery observers on cooperating commercial shark fishing vessels to observe the composition and disposition of the catch and by-catch. Monitoring of the southeastern United States shark fishery began in January 1994 and funding is in place through the summer of 2001. Data gathered in this program is utilized in developing management strategies for the fishery. Since the shark catch is headed, gutted and finned at sea, port sampling is not a viable means of quantifying the catch because the marketed carcasses are difficult, if not impossible, to identify to species. In addition, by-catch in the fishery is discarded at sea or used as bait and thus cannot be quantified at the dock. The CSFOP’s ground-truthing of the at-sea catch provides an invaluable source of information for both fishers and regulators alike. This accurate data, gathered by an unbiased team of academic observers, serves as a common starting point for management discussions during the regulatory process. Through the end of 2000, the CSFOP program monitored 6.7 million hook-hours of effort on 785 long-line sets, collecting biological data on 34 species and more than 35,000 individual sharks. The sandbar shark, (Carcharhinus plumbeus), a large coastal species, made up the majority of the overall catch (35.5 %), while a small coastal, the Atlantic sharpnose shark (Rhizoprionodon terraenovae), comprised 30% of the total catch. Overall, 61% of all sharks caught were landed and marketed, 21% were used for bait and 14% were tagged and/or released. CPUE (catch per unit effort) for large coastal species in three major fishing areas (Florida Atlantic coast, Florida Gulf coast and North Carolina) has shown a gradual increase since the inception of the program. Variation in catch composition and disposition has been observed from region to region. Off the Florida East coast, R. terraenovae represented 57% of the total catch while C. plumbeuscomprised 14.5%. By comparison, 33% of sharks caught off Florida’s Gulf coast were C. plumbeus and 18.5% were blacktip sharks (Carcharhinus limbatus). Off North Carolina,C. plumbeus dominated the total catch at 64% with R. terraenovae at 11.5%. For each region, the percentage of the total catch marketed was 68%, 71% and 80%, respectfully. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

The shark in modern culture: beauty and the beast

Sharks have always elicited a mixture of emotions in humans, ranging from fear and loathing to respect and admiration. Modern culture has been greatly influenced by mass marketing, as print and video media have become routinely accessible throughout much of the world. Sharks commonly are used in advertising campaigns where they often are portrayed as strong, fierce, and dangerous, or humorously lampooned as inept and cowardly. They frequently appear as protagonists in films and television shows, video and print cartoons, video games, and comic strips. Political cartoonists frequently portray politicians, lawyers and other seedy professionals as shark caricatures. The public image of sharks in North America has changed perceptibly in recent years as the mass media have begun to air natural history programming that presents a more balanced view of sharks featuring the words of contributing biologists and conservationists. (Session 26, Monday, July 9, Penn Stater, Room 207, 2:30)

A database of existing literature on the life histories of selected nearshore fishes of California 

As part of the Marine Life Management and Protection Acts, the California Department of Fish and Game (CDFG) must produce stock assessments and fishery management plans for fishes inhabiting nearshore habitats of California. We compiled a list of 124 nearshore fish species currently taken as part of California=s nearshore and live-fish fisheries, and analyzed the existing knowledge of their life histories (age, growth, maturity, longevity, habitat utilization, reproduction, recruitment, trophic relationships, and population/stock health, structure, and genetics) relative to their management and vulnerability. We thoroughly surveyed the existing literature, directed by a life history parameter questionnaire, and constructed a life history data matrix of the nearshore fish species on the list. Many gaps in the existing knowledge were identified, and specific research projects initiated on such subjects as age and size at maturity, age validation, genetics, and mobility of fish stocks subject to the nearshore fisheries of California. It is hoped that this project will be useful to those involved with the management of nearshore fisheries, and will be complimented by additions from future literature on the life histories of these fishes. It is available from the CDFG web site (www.dfg.ca.gov/Marine Resources) or from Nancy Wright (nmwright@dfg.ca.gov). (Session 4, Friday, July 6, Penn Stater, Room 206, 4:00)

Population dynamics of the finetooth shark, Carcharhinus isodon, in the northeast Gulf of Mexico

The population dynamics of the finetooth shark, Carcharhinus isodon, in the northeastern Gulf of Mexico were studied by determining age, growth, size-at-maturity, natural mortality, productivity, and elasticity characteristics of the population.

Von Bertalanffy growth parameters were estimated as

L_inf =1587 mm total length(TL),

K=0.23 yr – 1, and to 2.12 yr for females and 1352 mm TL,

K=0.38 yr – 1, and to =-1.48 yr for males.

The oldest aged specimens were 8.1 and 8.2 yr, and theoretical longevity estimates were 15.3 and 9.1 yr, for females and males, respectively. Median length at maturity was 1187 and 1230 mm TL, equivalent to 4.1 and 4.5 yr, for males and females, respectively. Instantaneous rates of natural mortality ranged from 0.598 to 0.848 when expressed as annual rates of survivorship. Rebound potentials averaged 0.037 yr-1 when the population level that produces maximum sustainable yield is assumed to occur at an instantaneous total mortality rate equaling 1.5M, and 0.066 yr – 1 when Z=2M. Mean generation lengths averaged 7 yr. Stage elasticities averaged 12.5% for age-0 survival, 49.7% for juvenile survival, and 37.8% for adult survival. In all, the finetooth shark exhibits population characteristics intermediate to those sharks in the small coastal complex and those from some large coastal species. (Session 3, Friday, July 6, Penn Stater, Room 207, 2:45)

Diel movement patterns of the Hawaiian stingray, Dasyatis lata, in Kaneohe Bay, Hawaii. 

The Hawaiian stingray, Dasyatis lata, is likely the most abundant benthic elasmobranch in nearshore Hawaiian waters. Acoustic telemetry was used to track the movements of seven rays in Kaneohe Bay, Oahu, Hawaii. Rays were tracked continuously over 50 hr periods. Geographical position was determined at 15-minute intervals during tracks, and was analyzed to determine space utilization and rate of movement. Rays were found to utilize significantly larger average activity spaces at night (0.83 – 0.70 km²) than during daylight hours (0.12 – 0.15 km²). Rates of movement were also significantly higher at night and crepuscular periods (p<0.001) than during the day. Mean total activity space for rays tracked was 1.32 km², and maximum swimming speed was approximately 1.9 km/hr. D. lata and juvenile scalloped hammerhead (Sphyrna lewini) pups in Kaneohe Bay show overlap in habitat use and time of activity; this may indicate competition for food resources. (Session 10, Saturday, July 7, Penn Stater, Room 207, 10:45)

Taxonomy of the Neotropical freshwater stingrays (Chondrichthyes: Potamotrygonidae). 

The Neotropical stingrays of the family Potamotrygonidae are confined to South American river drainages that flow into the Caribbean Sea or Atlantic Ocean. Even though frequently imported by the aquarium trade, species of the family remain poorly known in relation to their systematics and general biology. Factors that further complicate species identification are the great amount of intraspecific variation in color pattern and generally conservative meristic and morphometric features. Furthermore, many nominal species have been inadequately described in the literature and have poorly preserved type specimens. A revision of the family was initiated ten years ago, and to date at least four new species have been found. Although there is variation within species, coloration does distinguish some of them, and combinations of characters are ususally employed to separate species. A conservative estimate indicates the existence of 18 previously described valid species (in addition to the new species). This total may increase as some widespread species may require further subdivision. New species exist in all three valid genera (Potamotrygon,Paratrygon and Plesiotrygon), but primarily in Potamotrygon. This summary of the family was prepared originally for the CLOFFSCA project. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Comparative hearing sensitivity among free-swimming and bottom-dwelling elasmobranchs. 

Corwin (1978) found a correlation between size and structure of auditory anatomy and feeding strategies among elasmobranchs. Based on this correlation, he hypothesized that free-swimming elasmobranchs have more sensitive hearing than bottom-dwelling elasmobranchs. Hearing sensitivity, however, has rarely been explored in free-swimming elasmobranchs (n=2 carcharinids) or bottom-dwelling elasmobranchs (n=1 heterodontid), and has never been examined in skates or rays. For this project an audiogram was obtained for the little skate, Raja erinacea (Rajidae), using two methods, behavioral conditioning and auditory brainstem response (ABR). This audiogram was compared to those of free-swimming and bottom-dwelling elasmobranchs to elucidate the relationship between hearing sensitivity, auditory anatomy and feeding strategy. Results suggest that R. erinacea has less sensitive hearing than free-swimming elasmobranchs. The most sensitive hearing frequency of R. erinacea (200 Hz) is more than 20 dB re 1 Pa lower than the most sensitive hearing frequency of either of the free-swimming carcharinids (320 Hz). This corroborates Corwin&’s (1978) hypothesis, which was based on anatomical data. Anatomical auditory data, including the size of the macula neglecta and number of hair cells, will be obtained from R. erinacea and compared with Corwin&’s (1978) data to further test this relationship. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

On the origin of the English word shark and the Spanish tiburn

Sharks are conspicuously absent from the medieval bestiaries that described the known faunas and some imagianry animals as well. The reason for this omission is that large sharks were basically unknown until the voyages of discovery at the end of the 15th century. Medieval man fished rivers and the seashore and did not usually encounter large sharks. Both the Spanish and the English were familiar with the small sharks that inhabit their shores and had names for the small sharks, cazon and nuss respectively. When the Spanish encoutered large sharks in the Americas, they borrowed theCarib word tiburn to name them. The English later used the same word tiburn and used it through the 17th century. Later, in the late 1560&’s, the English borrowed the Mayan word xoc which means shark and tiburn disappeared from the English languaje. (Session 26, Monday, July 9, Penn Stater, Room 207, 9:30)

Reproduction in the smalltooth thresher shark, Alopias pelagicus off Baja California. 

The smalltooth thresher is an aplacental species that nourishes its embryos through oophagy (egg eating). The first two egg capsules produced by ovulating females contain a single egg, and one goes into each uterus. Egg capsules produced subsequently contain multiple eggs. Embryos star feeding on eggs very early in development. Embryos do not acquire the distended yolk stomachs that other lamnoid embryos have. There are at least two types of feeding egg capsules. Egg capsules produced late in gestation are about 20 times larger than those produced early in gestation. Embryos reach about 140-150 cm at birth. Embryos of all sizes can be found at any time, indicating that the species reproduces throughout the year. Only two young are produced per brood. (Session 10, Saturday, July 7, Penn Stater, Room 207, 2:00)

A New Genus and Species of Freshwater Stingray (Potamotrygonidae) from the Lower Amazon Drainage

The family Potamotrygonidae Garman, 1877 includes freshwater stingrays found in most river systems of South America. There are three known genera for this family: Paratrygon,Plesiotrygon, both monotypic, and Potamotrygon, including aproximately 21 valid species. Two specimens of an unidentified genus and species recently were captured (August 2000 and January 2001) in the State of Par, northern Brazil. One of the rays is a juvenile individual while the other, considering clasper calcification, possibly is a sub-adult. Both cannot be assigned to any of the known species or genera. The main dignostic charcteristics of this new genus and species are: relatively long filiform tail, lacking dorsal and ventral finfolds; absence of caudal sting; disc nearly circular with an anteromedian prominence; lack of a knob-shaped process on the external margin of spiracle and non-pedunculate very small eyes. This ray is locally known as maramass or aramass ray. It is considered by local fishermen less agressive than other, more abundant, potamotrygonid rays and probably is rare in this region. No dissection of these specimens was performed yet and data concerning internal aspects are being obtained by means of radiological techniques. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Demographic modeling under uncertainty: application to shark conservation 

Incorporating the effect of uncertainty and random variation in vital rates into demographic analyses is a useful approach that is increasingly being applied in conservation biology, but rarely used for marine taxa and not explored for sharks. This paper uses Monte Carlo simulation to calculate population growth rates (), generation times, and matrix elasticities for a suite of shark populations. The potential for population exploitation or recovery is also evaluated and the most vulnerable life stages identified using this probabilistic approach. Elasticity patterns for shark populations are linked to life-history characteristics to categorize those populations according to their likely response to perturbation of the various life stages. The 41 populations examined fall along a fast-slow continuum of life-history characteristics linked to stage elasticity patterns. Sharks with early age at maturity, low longevity, and large litter size have high  values and short generation times, whereas sharks that mature late, have high longevity, and small litter size have low  values and long generation times. Sharks at the fast end of the spectrum tend to have comparable adult and juvenile survival elasticities, whereas sharks at the slow end of the continuum have very high juvenile survival and fertility elasticities. (Session 3, Friday, July 6, Penn Stater, Room 207, 2:15)

Population structure of the blacknose shark (Carcharhinus acronotus) in the southeastern United States, based on mtDNA analysis 

We describe the results of genetic assays of blacknose sharks (Carcharhinus acronotus)sampled from the western North Atlantic and Gulf of Mexico. Mitochondrial DNA (d-loop control region) sequence variation was assayed in 160 individuals. This genetic variation was partitioned into within and among basin components. These components are used to address the null hypothesis that the two basins sampled do not harbor genetically distinct populations of blacknose sharks. Recommendations for conservation management are discussed. (Session 3, Friday, July 6, Penn Stater, Room 207, 4:30)

Portugal Distribution and abundance of Velvet Belly, Etmopterus spinax, and Smooth Lanternshark, Etmopterus pusillus, in the deepwaters of the Azores 

Sharks apparently play an ecological role of great relevance in the demersal community of the Azorean deepwaters. Two species are particularly significant, given their abundance and top predatory status in bottom waters deeper than 600m: Etmopterus spinax and E. pusillus. CPUE and size structure data collected from research cruise surveys on an annual basis are available for the Azorean main fishing grounds. However, no particular attention has yet been given to either species, since they hold no commercial relevance in the Azorean demersal fisheries. Trends on distribution, both geographical and bathymetrical, and abundance of Etmopterus spinax and E. pusillus are presented and discussed, in an attempt to shed some light on the ecological importance of both species in the Azorean deepwater domain. (Session 3, Friday, July 6, Penn Stater, Room 207, 1:45)

Behavioral and population studies of sixgill sharks (Hexanchus griseus) at a shallow water site using video and still imagery.

The bluntnose sixgill shark (Hexanchus griseus) is one of the largest of fishes, perhaps the most widely distributed vertebrate, and a top predator throughout its wide range. However, virtually nothing is known of its basic population biology or behavior. In British Columbia, this normally deep water shark is known to regularly frequent one shallow (20 m) reef (Flora Islets) in the Strait of Georgia where sixgill behaviour can be recorded using still and video imagery. A fully submersible time lapse video system was used to obtain quantitative data on the relative activity of sixgills at Flora as a function of time of year, time of day, tidal cycle, lunar cycle, water temperature, and illumination. A 3 camera stereo video system was used to obtain population size-frequency data by sex as well as measures of absolute swimming speed. Close-up 35 mm photographs were used to identify individual sharks based on distinctive scarring patterns. Resightings of these known individuals were used to study the time course of use of the reef by individuals and to provide a rough estimate of the size of the population of sixgill sharks that visit Flora in a particular year. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Thermal Tolerance Dynamics of Laboratory Acclimated and Field Acclimatized Atlantic Stingray, Dasyatis sabina

Physiological thermal tolerance adaptations of elasmobranchs are entirely unknown, while responses of bony fishes to temperature extremes have been exhaustively studied for over 100 years. We used critical thermal methodology to investigate laboratory and field temperature tolerance responses of nearly 400 Atlantic stingrays, Dasyatis sabina, from St. Joseph&’s Bay, Florida. Stingrays acclimated in the laboratory at temperatures between 11.6 and 37.0¡C had critical thermal maxima (CTMax) and minima (CTMin) ranging from 35.6 to 43.2¡C and 0.8 to 10.8¡C, respectively. For every 1.0¡C increase in acclimation temperature, heat tolerance increased 0.31¡C and cold tolerance decreased 0.43¡C. Fish could not be acclimated above 37.0¡C regardless of the rate or pattern of change in acclimation temperature. An ecological thermal tolerance polygon of CTMax/CTMin on acclimation temperature yielded a total area of 1247¡C² the second largest ever measured in a fish. Monthly CTMax and CTMin values of field acclimatized stingrays ranged from 37.6 to 41.8¡C and 2.6 to 6.6¡C, respectively. On average, CTMax values were 15.6¡C above, and CTMin values were 18.6¡C below, mean water temperatures. Our data demonstrate that Atlantic stingrays are remarkably eurythermic and well suited for inhabiting shallow inland bays and estuaries subject to dramatic diel and seasonal temperature changes. (Session 20, Sunday, July 8, Penn Stater, Room 207, 12:00)

From Icons to Art: The Cultural Significance of Sharks and Man 

Our goals in this symposium are two-fold: to trace the history of elasmobranchs&’ influence on human cultures through the use of art, and to understand how they are now perceived given how much we now know scientifically. Art is a somewhat unusual subject for a meeting like AES/ASIH. However, historically speaking, science and art were different aspects of the same discipline. Many great thinkers, iconoclasts, and renaissance men realized that the study of objects for representation in art requires amazing attention to detail and a fine understanding of both biological function and the organism&’s role in a larger system. Science and art, in this sense, become complementary and interchangeable. A focus of our symposium is the shark as the object of art, how that art has influenced human cultures, and how it reveals cultural perceptions to us. The symbol of the shark has also changed over time, and we will explore how the interplay between recent scientific ventures and modern forms of expressive media (modern art, news &’media&’, and public outreach and education) has affected the perception of sharks in our culture. (Session 26, Monday, July 9, Penn Stater, Room 207, 8:15)

Organochlorine contaminants and metabolites in elasmobranches: Have ecotoxicologists missed a susceptible animal?

Organochlorine contaminants (OCs) are industrial and agricultural chemicals (e.g., PCBs and DDT) that are an environmental concern because they are bioaccumulative, persistent and toxic. These chemicals have been shown to cause stress at the individual and population level in fish, birds, mammals and humans. Recently, metabolites of OCs, in particular halogenated phenolics compounds (HPCs), have been shown to be potent hormone mimics and potential endocrine disruptors. Although there is extensive data on OC levels and effects in wildlife there is almost no information on levels or effects of OCs and metabolites for elasmobranches. This is surprising because many elasmobranches occupy high trophic levels and may accumulate high levels of OCs through food web transfer and biomagnification. A recent measurement of OCs and HPCs in Greenland sharks (Somniosus microcephalus) showed this Arctic predator to be among the most contaminated organisms in the Canadian Arctic. High levels of HPCs suggest an active metabolic capacity in the sharks that requires further research. These results highlight the need to evaluate these chemicals in sharks, particularly those that feed in more contaminated regions of the world. (Session 16, Sunday, July 8, Penn Stater, Room 207, 8:15)

Organochlorine contaminants and stable isotopes of nitrogen and carbon in the Greenland shark (Somniosus microcephalus): Insights into the feeding ecology of the Arctic&’s only shark 

Organochlorine contaminants (OCs), stable isotopes of N (15N) and C  15C) and stomach contents were measured in 17 Greenland sharks (Somniosus microcephalus) and 4 turbot (Reinhardtius hippoglossoides) collected in the Davis Strait region to provide insight on the feeding ecology of this little studied shark. Values of  15N increased with shark fork length suggesting a shift to larger prey with growth. Stable isotope values place the Greenland shark at the same trophic level as the turbot and ringed seal but with a more pelagic source of carbon. However, more study should be undertaken to determine whether high tissue urea levels found in sharks influence 15N values, as this may underestimate shark trophic position. Concentrations of OCs (lipid basis) in Greenland shark were 10-100 and 3-10 X higher than those observed in turbot and ringed seals, respectively, suggesting a higher trophic level for the shark than implied by 15N values. Concentrations of  DDT in Greenland sharks are among the highest in Canadian Arctic biota, which may be related to low metabolism and a long life span. The presence of a ringed seal in the stomach of one shark, relatively high levels of oxychlordane in others, and high OCs concentrations suggest that seals may be a common prey item of Greenland sharks. (Session 7, Saturday, July 7, Penn Stater, Room 207, 8:30)

Electroreception in juvenile sandbar sharks, Carcharhinus plumbeus.

Sharks possess a sensory system, the ampullae of Lorenzini, which enables them to detect the bioelectric fields emanating from visually cryptic prey items. These electric fields are usually weak and either DC or of low frequency. This study quantifies the behavioral electrosensitivity of juvenile sandbar sharks, Carcharhinus plumbeus, to prey-simulating (2 cm dipole separation) and non-prey-simulating (>2 cm separation) fields. Electric field stimuli were varied in strength, size and sinusoidal frequency. Sharks responded to DC fields at field strengths between 10 and 150 nanovolts/cm (10 – 9 V/cm), as found for other species. Response rate (no. attacks/no. passes over a dipole) was proportional to field strength for both prey-simulating and non-prey-simulating stimuli. Sharks were exposed to dipoles of 2-20 cm separation, and showed no polarity preference at greater electrode separation. Sharks oriented to AC fields between 5 Hz and 10 kHz, although preliminary data show they are unable to detect frequency information above 50 Hz. The results indicate that juvenile sandbar sharks are capable of detecting a broad range of electric fields, including those of large dipole separation and high frequency, which may be important for behaviors other than foraging. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Hibernating, hiding or hanging out – what do basking sharks (Cetorhinus maximus) do in winter?

Basking sharks occur throughout New Zealand, and are seen inshore mainly in spring-summer. 208 sharks were recorded by scientific observers aboard trawlers over 10 years, with up to 14 sharks caught per tow. Most captures came from the hoki and barracouta fisheries off Banks Peninsula (EC), the hoki fishery off the west coast South Island (WC) and the squid fishery around the Snares and Auckland Islands (SA). The EC and SA fisheries catch sharks in spring-summer, whereas the WC fishery catches them in winter. Sharks were caught mainly in 100-300 m in SA, 100-600 m in EC and 500-800 m in WC. There is some evidence that sharks are taken mainly on or near the bottom. Most WC and SA sharks were males 7-8 m long. The EC fishery had a more even sex ratio, and a high proportion of immature sharks (4-6 m long). Few large females were recorded. Winter catches of sharks in WC at depths up to 800 m explain their absence from shallow coastal waters at this time. We suggest that basking sharks do not hibernate on the seabed in winter, but remain active on the upper continental slope. (Session 7, Saturday, July 7, Penn Stater, Room 207, 9:15)

The ultimobranchial gland and calcitonin production in the Atlantic stingray,Dasyatis sabina.

In elasmobranchs, the ultimobranchial gland (UBG) is a paired organ situated between the dorsal musculature of the pericardial cavity and the ventral pharyngeal epithelium. The UBG consists of small round follicles with cuboidal or columnar epithelial walls and central lumina. Parenchymal cells of the UBG produce calcitonin, a 32-amino acid peptide hormone that is best known for its role in protecting the mammalian skeleton from demineralization. In an effort to elucidate the role of this phylogenetically ancient hormone in elasmobranchs, the present study investigated changes in tissue architecture and calcitonin production in the UBG of the Atlantic stingray, Dasyatis sabina, associated with sex, season, reproductive status, and environmental salinity. In addition, data on immunoreactivity of calcitonin in tissues and secretions of D. Sabina are presented to clarify target organs of calcitonin action. (Session 20, Sunday, July 8, Penn Stater, Room 207, 2:30)

The Reaction between Underwater Electrical Equipment and Elasmobranchii.

The increase in the quantity and types of electrically powered underwater apparatus and instrumentation is exposing marine life to increasing electromagnetic (EM) radiation. This equipment is used by both recreational and commercial users of the marine habitat. The Elasmobranchii (sharks, rays and skates) have sensory organs which detect weak electric fields for hunting and possibly navigational purposes. This presentation describes the initial results of a research program to investigate the electric fields produced by underwater electrical equipment and to relate these to the Elasmobranchii’s sensitivity. Underwater observations, with two video clips, indicating both distress and interest by sharks to underwater EM radiation are discussed together with measurements of electric fields from electrical apparatus. The initial findings indicate that underwater electrical apparatus do adversely influence the Elasmobranchii. Further research should be conducted to quantify this influence and determine methods to shield the apparatus in order to prevent the radiation of EM fields and the resultant possible decline in marine resources and tourist potential. (Session 16, Sunday, July 8, Penn Stater, Room 207, 9:15)

Regulation of body temperature in the salmon shark, Lamna ditropis.

The salmon shark, Lamna ditropis, occurs in the boreal and cool temperate coastal and oceanic waters of the North Pacific Ocean. As with all other members of the Family Lamnidae, they are known to be endothermic based on their possession of vascular countercurrent heat exchangers (retia mirabilia). Previous body temperatures obtained from moribund and recently killed specimens showed elevations ranging from eight to 15.6^oC over sea surface temperature. We present results from over 50 hours of temperature telemetry data obtained from four free-swimming salmon sharks. This species displayed a very high thermoregulatory ability, maintaining an average body temperature of 25.3^o C in ambient water temperatures ranging from just over five to 16^o C. Depth distribution ranged from the surface to over 140 m. (Session 20, Sunday, July 8, Penn Stater, Room 207, 11:45)

Growth dynamics of female salmon sharks in the eastern and western North Pacific: a spatially structured population?

The salmon shark, Lamna ditropis, occurs in the boreal and cool temperate coastal and oceanic waters of the North Pacific Ocean. In the eastern North Pacific, we found adults of this species typically ranged in size from 200-260 cm TL and weighed upwards of 220 kg. To date, our study shows that maximum age is 20 for females with a growth coefficient (k) of 0.187. Our results show that female salmon sharks in the eastern North Pacific possess a faster growth rate, reach sexual maturity earlier, have greater longevity, and attain greater length and weight than those living in the western North Pacific. The variability in these life history parameters may be due to ecological differences between the eastern and western North Pacific or due to population structure. North-south migrations are fairly well documented in salmon sharks, while cross-Pacific migrations are suspected. (Session 3, Friday, July 6, Penn Stater, Room 207, 2:30)

The Megatooth Shark: Myth, History, and Science

The public’s fascination with the fossil megatooth shark Carcharodon megalodonapproaches that seen for dinosaurs. Much of this revolves around its tremendous size: the megatooth reached a length of ca. 16 meters (52 feet), making it the most spectacularly large Mio/Pliocene marine predator. C. megalodon is primarily known only from teeth (and occasional vertebral centra). Renaissance accounts held that its large, triangular teeth were the petrified tongues, or glossopetrae, of dragons and snakes, an interpretation corrected in the 1600s by the great early naturalist Steno, who recognized them as ancient shark teeth (and famously produced a rather grotesque depiction of a shark’s head bearing such teeth). Since Steno’s time, many attempts—some fanciful, others more realistic—have been made to reconstruct the megatooth. Modern reconstructions have generally used the extant Great White Shark C. carcharias as a starting point, recognizing that the two forms are related (although some have questioned just how closely). One stubborn bit of megatooth folklore is that it is still living, lurking like the coelacanth in cryptic deep-sea environments—this persists despite the lack of any physical evidence, and the improbability of a 50-foot-long shark, which consumes large coastal prey, somehow remaining undetected. (Session 26, Monday, July 9, Penn Stater, Room 207, 1:30)

Preliminary trophic model of a lemon shark (Negaprion brevirostris) nursery at Bimini, Bahamas 

The North Sound, Bimini, Bahamas, is a highly enclosed, mangrove-fringed, sub-tropical lagoon which functions as a nursery for approximately 75 juvenile lemon sharks Negaprion brevirostris. Despite low species diversity and reduced water quality due to restriction of tidal flow, the nursery appears to be a stable and adequate environment for the early development of lemon sharks. A preliminary trophic model using the Ecopath 3.0 software is presented. Estimates are calculated of guild trophic position, ecotrophic efficiency, omnivory index, flow to detritus, respiration, niche overlap, electivity and trophic impacts. Whole ecosystem parameters estimated include total and guild energy throughput, trophic level transfer efficiency, Finn’s recycling index, ascendancy, system overhead and system capacity. Additionally, all trophic pathways are tabulated. Knowledge of guild and ecosystem parameters will reveal how the nursery functions to support the lemon sharks, identify vulnerable components, and indicate the level of system stability and maturity. An energy flow model will also be elaborated to assess the capacity of the North Sound with respect to the production of lemon sharks. This in turn will provide an estimate for the recruitment of sub-adults into the general population, and indicate levels of sustainability within the nursery. Funded by the Florida State Department of Education. (Session 7, Saturday, July 7, Penn Stater, Room 207, 8:45)

A meta-assessment for elasmobranchs based on dietary data and Bayesian networks 

Meta-assessments are models enhanced by the incorporation of other stock assessment results. We used this idea to estimate historic biomass trends for demersal elasmobranchs of the Irish Sea. Bayesian networks, constructed from published dietary data and resembling food webs, allowed us to incorporate into our estimates the results from virtual population analysis (VPA) for Irish Sea cod, sole, plaice and whiting. To assess accuracy, we used cross-validation, estimating historic biomass trends in each individual VPA species from trends in the other three plus trends in fishing effort. We compared predicted annual trends to those derived from VPA and found 66% accuracy. We also compared biomass trends estimated from annual trawl surveys to corresponding network predictions, recovering survey trends correctly 61% of the time for elasmobranchs, 78% of the time for gurnards (Triglidae) and 89% for bib and pout (Trisopterus spp.). Results suggest that of the 11 elasmobranchs examined, the angel shark (Squatina squatina) suffered the most from 1987 to 1997, a view consistent with survey results. Our approach also suggested a marked decline in common skate (Dipturus batis) over the period 1965-1978, during which time the skate was extirpated from the Irish Sea. We conclude that meta-assessment can serve as a useful tool for the preliminary identification of threatened stocks. (Session 3, Friday, July 6, Penn Stater, Room 207, 3:30)

Contaminants in Sharks of the South Atlantic Bighty: An Assessment of Pesticides and PCBs in Shark Livers as an Environmental Risk 

Charleston, South Carolina is surrounded by abundant marshes and estuaries that serve as potential sinks for contaminants, but are also nursery grounds for abundant species of fish, including sharks. Top level predators such as sharks may be used as bioindicators of coastal environmental health since they are known to accumulate persistent chemical contaminants. This research involved analyzing the livers of sharks [Atlantic Sharpnose (Rhizoprionodon terraenovae), Blacknose (Carcharhinus acronotus), and the Bonnethead (Sphyrna tiburo)] caught in near-shore coastal waters in Charleston, SC, and documenting the levels of lipophilic contaminants, including polychlorinated biphenyl’s (PCB’s) and chlorinated pesticides. Sharks were collected by longline, measured for total and fork length, and sexed on board. Sharks within each species fell into three size classes: pup, juvenile and adult. The whole liver was removed, iced, and brought to the laboratory, where 1-gram sub-samples were taken. Each liver sample was extracted using Accelerated Solvent Extraction, and the lipid was removed from the analytes of interest by size exclusion chromatography. The analyte levels were determined using gas chromatography/mass spectroscopy and reported as ng/g lipid. Results indicated the presence of PCB’s and persistent organochlorine pesticides in each species of shark studied. Size, life stage and species differences will be discussed. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

The behavior and ecology of tiger sharks in a subtropical seagrass ecosystem 

Tiger sharks (Galeocerdo cuvier) are apex predators in a variety of nearshore ecosystems throughout the world, but relatively little is known about how they function in these systems. From 1997-2000, we conducted studies of the behavioral ecology of tiger sharks and their prey in Shark Bay, Western Australia. Tiger sharks were the most commonly caught species of large shark in the bay, but were not present in all seasons. Tiger shark catch rates were highly correlated with water temperature, but were also correlated with the seasonal occurrence of their main prey. The importance of seagrass grazers (turtles and dugongs) in the diet of tiger sharks suggests the possibility that these sharks may influence community structure through trophic interactions. Tiger sharks may also be important in this community because of their influence on habitat use decisions by their prey species. Our studies of habitat use by tiger sharks and their prey suggest that habitat use decisions by these species may result in indirect behavioral effects, and that tiger sharks may mediate these effects. Ongoing studies in Shark Bay will continue to elucidate the role of tiger sharks in seagrass ecosystems. (Session 7, Saturday, July 7, Penn Stater, Room 207, 9:00)

Randomization techniques for analyzing habitat preferences from tracking data Acoustic tracking has been widely used in studies of elasmobranch movements and habitat use. 

However, it is often difficult to determine how often individuals should use a particular habitat in the absence of a preference. This results in difficulties conducting appropriate statistical tests of habitat use to determine whether there is a significant habitat preference. Many difficulties can be overcome by employing a variety of randomization techniques to data analysis. We will present three different randomization techniques: correlated random walk, within track randomization, and randomization of a sample of tracks. Each of these techniques has a unique set of underlying assumptions and can be used to answer different questions. The differences among techniques will be illustrated with analyses of both computer-generated tracks with known habitat preferences and movement biases and empirical tracking data from tiger sharks (Galeocerdo cuvier). In general, the sample randomization is ideal for looking at the overall preference of a sample or differences in habitat use among subsamples (e.g. sex-classes). However, the correlated random walk and within track randomization allow analysis of individual habitat preferences, and may be more appropriate for some research questions. (Session 10, Saturday, July 7, Penn Stater, Room 207, 10:30)

Comparison of home range estimates by passive monitoring and active tracking techniques 

An array of 24 data-logging acoustic hydrophones was deployed in a known shark nursery area on the central Gulf coast of Florida to monitor the movements of juvenile blacktip sharks, Carcharhinus limbatus. During the summer of 2000, 33 C. limbatus were monitored via the automated array. An additional four sharks were actively tracked for periods of 24-hours each to define their short-term movement patterns. Results from the array allowed home range estimates to be determined for all individuals monitored. Sharks were monitored for periods of 2 – 167 days. Weekly, monthly and cumulative home range areas were estimated for seven sharks using minimum convex polygon and fixed Kernel home range estimators. Daily home ranges were also calculated for actively tracked animals using minimum convex polygon and fixed Kernel home range estimators. For purposes of comparison, a daily home range estimate was calculated for five sharks monitored by the array on the same day of each of the manual tracks. An extrapolated randomization of manual tracks was also completed to allow weekly and cumulative home range estimates to be calculated based on active tracking data. The results of all home range estimates and the comparison of results among techniques will be discussed. (Session 10, Saturday, July 7, Penn Stater, Room 207, 11:45)

Are Inshore, Shallow Water Nursery Areas Energetically Demanding for the Atlantic Sharpnose Shark, Rhizoprionodon terraenovae in the Northern Gulf of Mexico?

The inshore waters surrounding the extensive barrier island system off the coast of Mississippi have been identified as an important nursery ground for several shark species including the Atlantic sharpnose shark. Annually, sharpnose sharks migrate into these waters in the early spring and in the fall migrate to offshore warmer waters. Seasonal changes in environmental parameters in the inshore habitat, specifically temperature, may affect the energy budget in this species. The objective of this study was to determine if the energetic condition of the sharpnose shark changes seasonally while they inhabit the inshore nursery area. Two indicators of energetic condition were used in this study, condition factor and hepatosomatic index, as well as a direct measurement of total energy content by the use of bomb calorimetry. A significant seasonal change in the energetic condition was found to occur in the sharpnose shark while they inhabited these nursery areas. The energetic condition of these sharks was high when they moved inshore in the spring, decreased during the summer months and increased to higher levels in the fall. Inshore, shallow water nursery areas in the northern Gulf of Mexico appear to be energetically demanding for the Atlantic sharpnose shark during the summer. (Session 20, Sunday, July 8, Penn Stater, Room 207, 11:15)

Identification and Characterization of Shark Nursery Grounds of the Northern Gulf of Mexico.

From October 1997 until September 2000 we conducted a survey of shark nursery grounds along the Mississippi and Alabama coasts. Our objectives were (1) to identify shark nursery/pupping areas in the northern Gulf of Mexico, (2) to compare abundance and diversity of sharks between sites, seasons and years, and (3) to characterize the nursery areas in terms of environmental parameters. Sampling was conducted using gill nets fished from 1500 to 2200 hours from March to October each year of the study. At each sampling station environmental data was recorded. All sharks collected were identified to species, sexed, measured (total length), and, when possible, tagged and released. In 1998, 1999 and 2000 we collected 522, 517 and 1650, while tagging 300, 300, and 700 sharks, respectively. The most abundant species were found to be Rhizoprionodon terraenovae,Carcharhinus limbatus, and Carcharhinus isodon. Other species collected wereCarcharhinus leucas, Sphyrna tiburo, Carcharhinus acronotus, Sphyrna lewini,Carcharhinus brevipinna and Carcharhinus plumbeus. Nursery grounds were identified in a number of areas along the coasts of Mississippi and Alabama. Most notably, the Mississippi Sound and the waters surrounding the barrier islands serve as important habitat for neonates and juveniles of all of the above species. (Session 3, Friday, July 6, Penn Stater, Room 207, 1:30)

Sharks and rays attracted to offshore oil and gas platforms in the Gulf of Mexico.

Offshore oil and gas platforms can function as fish attracting devices (FADs) for a variety of marine fishes, including elasmobranchs. Sharks and rays may use these structures as refuges, as core areas for daily activities, or as areas to feed on natural prey or anthropogenic food (bait, offal). In the shallows surrounding platforms in the Gulf of Mexico, sharks such as the silky shark (Carcharhinus falciformis), scalloped hammerhead (Sphyrna lewini) and whale shark (Rhincodon typus) and rays such as the spotted eagle ray (Aetobatus narinari) and the Atlantic manta (Manta birostris) have been frequently observed, photographed and videotaped. Some pelagic elasmobranchs such as the silky shark appear to use these structures as core areas for juvenile stages. In the deep waters (>300 m) surrounding the structures, elasmobranchs such as sixgill sharks (Hexanchus spp.), gulper sharks (Centrophorus spp.) and skates (Raja spp.) have been recorded by ROV-mounted video cameras deployed from the structures. Shallow and deepwater video of these various elasmobranch species around Gulf of Mexico platforms will be shown. The potential impacts of the offshore oil and gas structures on elasmobranch populations will be discussed in relation to the emerging trend of deeper structures being deployed in the oceans. (Session 16, Sunday, July 8, Penn Stater, Room 207, 9:00)

Shark Feeding Dives: Are They All Bad?

Shark feeding dives have come under attack as being detrimental to the health and ecology of sharks and the marine environment, a threat to diver safety, and a source of user conflicts. Wildlife conservationists caution that feeding wild animals always has negative consequences, and resource managers have been receptive to banning shark feeding dives altogether on general principle. What has been missing in the discussion are any real scientific data on the effects of these dives, which in some areas have been operating consistently for 15-20 years. Effects on the behavior, health, ecology and life history of fed sharks can be classified as certain, probable, or possible, and these will be discussed in light of the minimal scientific information that exists. Possible effects on the marine environment also will be examined with what little data exist. Diver safety will be addressed using records of the Bahamas Diving Association compiled since 1973, indicating the dives have been relatively safe for customers but have carried higher risks in recent years for staff. These various effects will be weighed against the positive benefits of the dives, which under certain circumstances have included advances in public education, scientific research, and conservation measures on sharks. (Session 16, Sunday, July 8, Penn Stater, Room 207, 10:30)

Isolation and preliminary characterization of a collagenase/gelatinase inhibitor from shark cartilage 

Angiogenesis, the process of new blood vessel formation, is essential for the uncontrolled growth of solid tumors, and facilitates the metastasis of transformed cells. Inhibitors of angiogenesis hold great promise in the search for improved cancer therapies. During angiogenesis, the successful migration of endothelial cells from the vasculature to a focus of developing tumor cells depends upon the proteolytic activity of matrix metalloproteases (MMPs) to degrade the basement membrane of the parent vessel and the extracellular matrix. Inhibitors of these enzymes have been shown to inhibit angiogenesis. We show that high salt extracts of cartilage from several shark species, including bull Carcharhinus leucas, lemon Negaprion brevirostris, and nurse Ginglymostoma cirratum, contain collagenase/gelatinase inhibitory activity. From such extracts, a protein that inhibits gelatin degradation by the mixture of MMPs secreted by A2058 human malignant melanoma tumor cell line has been isolated. The partially purified inhibitor is heat stable in the absence of a reducing agent, and has an approximate molecular weight of 20 kD, as determined by both size exclusion chromatography and SDS polyacrylamide gel electrophoresis. Isoelectric focusing indicates the inhibitor is a basic protein, with a pI of approximately 9.0. The potential anti-angiogenic activity of the inhibitor is currently being investigated. (Session 20, Sunday, July 8, Penn Stater, Room 207, 1:30)

The reproductive biology of the porbeagle shark, Lamna nasus, in the western north Atlantic ocean 

Reproductive organs from 393 male and 382 female porbeagles, Lamna nasus, caught in the western North Atlantic Ocean, were examined to determine size at maturity and reproductive cycle. Males ranged in size from 86 to 246 cm fork length (FL) and females ranged from 94 to 288 cm FL. Maturity in males was best described by an inflection in the relationship of clasper to fork length when combined with clasper calcification. Males matured between 162 and 185 cm FL with 50% mature at 174 cm FL. In females, all internal organ measurements related to body length showed a strong inflection around the size of maturity. Females matured between 209 and 231 cm FL with 50% mature at 218 cm FL. After a protracted fall mating period (September – November), females give birth to an average of 3.9 young in the spring (March – June). As in other lamnids, young are nourished through oophagy. Evidence from this study indicates a one year reproductive cycle with gestation lasting 8-9 months. (Session 10, Saturday, July 7, Penn Stater, Room 207, 2:15)

Electroreception in carcharhinid and sphyrnid sharks

The unique head morphology of sphyrnid sharks might have evolved to enhance electrosensory capabilities. The enhanced electrosensory hypothesis is tested by comparing the behavioral responses of carcharhinid and sphyrnid sharks to prey-simulating electric stimuli. Juvenile scalloped hammerhead and sandbar sharks orient to dipole electric fields from approximately the same distance (25-30 cm) and thus demonstrate comparable threshold sensitivities (<5 nV/cm). Despite the similarity of response threshold, the orientation pathways and behaviors differ for the two species. Hammerheads typically demonstrate a pivot orientation in which the edge of the cephalofoil closest to the dipole remains stationary while the shark bends its trunk to orient to the center of the dipole. In contrast, sandbar sharks orient with a lateral head snap to bite at the dipole. The different orientation types are attributable to the hydrodynamic properties of the cephalofoil, which enable the hammerheads to execute sharp turns at high speed. The greater trunk width of the sandbar sharks prevents them from demonstrating the same degree of flexibility. Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to dipole electric fields, it does provide i) a greater lateral search area, which may increase the probability of prey encounter, and ii) enhanced maneuverability, which may aid in prey capture. (Session 7, Saturday, July 7, Penn Stater, Room 207, 9:30

A genetic investigation of philopatry in blacktip sharks (Carcharhinus limbatus)utilizing continental nurseries along the U.S. Atlantic and Gulf of Mexico coasts: preliminary results using mitochondrial control region haplotypes.

Blacktip sharks (Carcharhinus limbatus) are a highly migratory elasmobranch species with large populations occurring along the U.S. south Atlantic coast and the Gulf coasts of the U.S. and Mexico. Tagging and tracking studies conducted by Mote Marine Laboratory have suggested philopatric behavior in C. limbatus populations located in coastal areas of the Gulf of Mexico. The present study investigated natal site fidelity, a form of philopatry, within blacktip populations based upon haplotype frequencies among five continental nursery areas. Haplotype frequencies were determined by manually sequencing the entire mitochondrial control region (approximately 1068 bp) of 30 neonates from each of three nursery areas on the central Gulf coast of Florida, 30 neonates from the western Gulf coast of Mexico and 8 neonates from the Atlantic coast of South Carolina. If female blacktip sharks in these regions are philopatric for their natal nursery areas, a significant difference in mtDNA haplotype frequencies should be present among nurseries as a result of genetic drift. (Session 3, Friday, July 6, Penn Stater, Room 207, 4:00)

Development of the electric organ of Raja eglanteria 

The electric organ of Raja eglanteria consists of paired, longitudinal columns of disc-shaped electrocytes within the lateral musculature of the tail. Although it is known that electrocytes develop from embryonic hypaxial muscle fibers, little information exists on the stages of this differentiation process. Examination of H&E stained paraffin sections through the tail of skate embryos sampled at weekly intervals (hatching occurs around week 12) and at 3 months post-hatching reveals that each electrocyte develops from a single skeletal muscle fiber. Electroblasts, or immature electrocytes, are first identified during the 5th week of development and are distinguished from their skeletal muscle precursors by an increase in number of nuclei and a shortening of fiber length. As development proceeds (weeks 6-8) electroblasts continue to shorten as the rostral end expands to form a club-shaped cell. By the 10th week of development, a further expansion of the rostral end and regression and thinning of the caudal end results in the formation of a thick, transversely oriented disc-like cell which closely resembles a structurally mature disc-shaped electrocyte. Further development of electrocytes involves expansion and thinning of the disc in the transverse plane. Electrocytes are fully differentiated by 3 months post-hatching. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

A history of elasmobranchs in public aquariums and their impact on public perception: from visual imagery to swimming visuals 

Prior to the opening of public aquariums in the second half of the 19^th century, inhabitants of temperate latitudes had little chance of encountering elasmobranchs beyond the fish market, and certainly very few were lucky enough to see one alive. The only means of visualizing an elasmobranch was through illustrations in the scientific literature, artistic renditions, or sensational reports in the popular press. These sources were not at all times entirely accurate. Even scientific illustrations perpetuated earlier misconceptions of elasmobranch morphology. The opening of public aquariums dispelled many of the myths surrounding these fish. Sharks, skates and rays were displayed in public aquariums at Berlin (1869), Frankfurt (1872), Brighton (1872), Naples (1874), Hamburg (1884), Plymouth (1888), Helgoland (1892), Rovigno (1892), New York (1896), and Monaco (1905). Species regularly displayed included Scyliorhinus canicula, Scyliorhinus catulus,Squatina angelus, Squalus acanthias, Galerohinus galeus, Pristiurus malanostomus Mustelus laevis, Trigon sp., Torpedo oculata, Torpedo marmorata, Raja spp. By 1920, over 45 aquariums were drawing 10 million visitors a year. The public perception of sharks, skates and rays slowly evolved during this period, not only because of direct exposure to live fish, but also because of novel observations on elasmobranch biology by watchful attendants. (Session 26, Monday, July 9, Penn Stater, Room 207, 2:00)

The art of illustrating elasmobranchs 

Sixteenth to nineteenth century expeditions to the subtropical and tropical new world and beyond returned to Europe with astounding discoveries of animal and plant species, many of which were either preserved or brought back alive. Transporting elasmobranchs alive was impossible and preserving them was impractical. Expedition naturalists had to sketch fresh specimens, thereby capturing their natural shape and colors, in order to lend credence to the existence of these exotic fish. Many of these illustrations were gross misconceptions and clearly not drawn from life, others were accurate and wonderful renderings. As scientific illustration became the necessary norm in the 19^th century, morphological accuracy became more important than artful execution. Many scientists and emerging professional illustrators incorporated masterful techniques while at the same time maintaining precise portrayals. The transition from fanciful renditions to anatomically accurate and artistically satisfying illustrations of elasmobranchs eventually gave way to a workmanlike iconographic style in the 20^th century. This is pedantic and abbreviated illustrative technique seems to be giving ground to a renaissance of the more pleasing styles of the late 1800’s and early 1900’s. An historical narrative on the artistic and not, accurate and erroneous, portrayals of elasmobranchs will be delivered. (Session 26, Monday, July 9, Penn Stater, Room 207, 12:00)

Preliminary studies of allograft rejection in juvenile clearnose skates Raja eglanteria 

As part of our effort to characterize cell mediated immune function in elasmobranch fishes, studies to examine rejection responses to skin autografts and allografts using juvenile clearnose skates Raja eglanteria were initiated. Approximately 1 cm² sections of skin were removed from the dorsal surface of donor animals and transplanted either to the same animal (autograft, n= 8) or to unrelated animals of the same species (allograft, n= 9). Skin grafts were photographed weekly for the first eight weeks, then biweekly for up to eighteen weeks. Visible responses were evaluated in terms of progressive infiltration by pigmented cells, relative inflammation, and general appearance of the graft. Grafts were biopsied weekly for eight weeks, and the presence of potential B- and T-lymphocytes were visualized by RNA in situ hybridization using riboprobes specific for immunoglobulin and T-cell receptor antigen genes. Autografts were accepted within three to four weeks while allografts were chronically accepted over times ranging from four to eight weeks. None of the allografts was rejected. These preliminary findings with R. eglanteria contradict results of three earlier reports demonstrating chronic (6-7 week) rejection of skin allografts using shovelnose guitarfish Rhinobatos productus, southern stingray Dasyatis americana, and horn shark Heterodontus francisci. (Session 20, Sunday, July 8, Penn Stater, Room 207, 1:45)

Infertility in Bonnethead Sharks, Sphyrna tiburo, in the Eastern Gulf of Mexico May Be Caused by Endocrine Disrupting Chemicals in the Environment 

Previous studies have demonstrated a high frequency of infertile ova in the uterus of pregnant bonnethead sharks along the central Gulf coast of Florida. We hypothesized that this infertility was caused by disruption to the endocrine system and that this infertility could be correlated with the presence of environmental contaminants, especially organochlorines. To test these hypotheses, we collected samples from bonnethead sharks from three areas that represented three different levels of organochlorine contamination. These included Florida Bay in the Florida Keys (the least contaminated control area), Anclote Key near Tampa Bay (highly contaminated area), and Apalachicola Bay in the Florida Panhandle (intermediate contamination). Differences were found in serum concentrations of reproductive steroid hormones, sperm counts and sperm viability, concentrations of various organochlorines, growth and reproductive parameters, and resultant population intrinsic rates of increase. Estradiol concentrations in mature females from Tampa Bay were found to be one half the concentrations found in the Florida Bay (control) females. There were significant differences in serum concentrations of estradiol and testosterone from immature females (Tampa Bay << Florida Bay). It is likely that these differences in hormone concentrations are caused by endocrine-disrupting organochlorine compounds present in the marine environment inhabited by these sharks. (Session 16, Sunday, July 8, Penn Stater, Room 207, 8:45)

Cortisol Mediated Movement in the Sedentary Coral Reef Fish (Dascyllus albisella) 

Cortisol has long been recognized as a ªstress hormone in vertebrates and has been implicated in dominance and social behavior in fish species. In this study, we propose that the reception of agonistic behavior in the damselfish Dascyllus albisella can result in elevated levels of cortisol, which in turn trigger migration out of their social group. To test whether cortisol induces movement in D. albisella, we exposed individuals to a cortisol-seawater solution and compared their movement behavior over time (within a 3 x 2 cells grid) in 380 l aquaria against untreated control fish. We found that both treatment and time elapsed from removal of treatment had effects on the movement rate of individuals. However, there was no interaction between the two factors. Cortisol treated fish moved between cells more often than control fish during the observation periods and thus spent less time than control fish in any given cell. While not a definitive study, our results suggest that this is an appropriate direction for further study. (Session P-32, Monday, July 9, Penn Stater, Deans Hall)

Mechanism of inflation behavior in the swellshark, Cephaloscyllium ventriosum(Elasmobranchii: Scyliorhinidae) 

Numerous lower vertebrates (e.g., chuckwallas, Sauromalus obesus) are capable of defensive inflation, whereby an increase in body volume affords some anti-predatory advantage. Sharks of the genus, Cephaloscyllium, are also reported to exhibit inflation behavior, although the morphological and physiological details were not previously described. The northeastern Pacific species, C. ventriosum, was therefore studied to i) determine the mechanics of the inflation response, ii) identify any associated anatomical modifications, and iii) elucidate the ecological significance of this atypical elasmobranch behavior. Whole body radiographs of deflated and inflated specimens were performed to confirm the body region responsible for housing the engulfed medium and describe general differences between the deflated and inflated states. Swellsharks were also induced to inflate in a novel experimental aquarium after surgical implantation of miniature pressure transducers in the cardiac stomach as well as buccal and parabranchial cavities. Digital footage of inflation events was taken to correlate external phenomena related to inflation with recorded internal pressure changes. A model of inflation behavior is advanced that explains how super-ambient pressures are created within the buccal cavity in order to force water through the esophagus and into the fore portion of the stomach. (Session 29, Monday, July 9, Penn Stater, Room 105, 8:30)

Sharks in land. The symbolism of freshwater sharks and sawfishes in north Australian Aboriginal societies

An important metaphor in Aboriginal religion is that of rivers flowing to the sea. Rivers link the lands of independent cultures and clans, symbolizing social alliances, profound knowledge, and the soul&’s journey in death. Family groups trace their origin to supernatural ancestral beings (totems) who often assumed the form of animals. During epic journeys, these ancestors shaped the landscape, created humanity, and bestowed land and culture upon their descendants. Revered for their euryhaline power, carcharhinid sharks and sawfishes appear prominently as ancestral creators of river systems throughout Arnhem Land, and are associated with concepts of diplomacy, rites of passage, and lawful vengeance. While each sacred site founded by ancestral sharks is owned by a distinct cultural entity, the disparate clans owning estates along the shark&’s path recognize a shared heritage as children of their shark mother. In tracing the origin of human social groups to facets of the natural world, totemic ancestry empowers Aboriginal people to recognize personal kinship ties to virtually any natural species, members of other totemic societies, and even to the land itself. As the embodiment of the sacred rivers which they created, euryhaline sharks remain central religious symbols in Arnhem Land societies. (Session 26, Monday, July 9, Penn Stater, Room 207, 9:00)

Reproductive biology of gulper sharks from the Cayman Trench, Jamaica

Gulper sharks (Centrophorus: Squalidae: Squaliformes) typically are gray to brown, with large green eyes, spines anterior to both dorsal fins, and pectoral fins that often have a free rear tip that extends well under the first dorsal origin. They are most abundant below 200 meters depth. Specimens were obtained via horizontal longline at depths between 400-900 meters. The reproductive biology of 6 male and 38 female Centrophorus cf. uyato have been examined. The smallest mature male was 81.2 cm total length whereas the smallest mature female was 91.5 cm total length. The sharks exhibit aplacental viviparity with a maximum of two pups per litter. Ova continued to develop throughout gestation. Most females carrying developing embryos had two large (>4.9 cm), equally developed ovarian ova, which leads us to believe that they ovulate soon after parturition. This species seems to exhibit complete sexual segregation during the non-mating season with males being completely absent from the study site during the summer months. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Are elasmobranchs susceptible to dioxins?

Anthropogenic pollutants in marine environments include many planar halogenated aromatic hydrocarbons (PHAH). These compounds are toxic and carcinogenic, and bioaccumulate in elasmobranchs. The toxic effects of TCDD (2, 3, 7, 8-tetrachlorodibenzo-p-dioxin) and related PHAHs (e.g., non-ortho-substituted PCBs) are mediated through the aryl hydrocarbon receptor (AHR) pathway. Differences in ligand binding affinity of AHRs underlie some species- and strain-specific differences in the toxicity of TCDD. Objectives are to clone and characterize AHRs in elasmobranchs and to assess their TCDD-binding affinity. We used reverse transcription polymerase chain reaction (RT-PCR) with degenerate primers to isolate fragments of the AHR. Previous work in this lab identified partial sequences of two forms of the AHR from spiny dogfish Squalus acanthias and smooth dogfish Mustelus canis, and one AHR from little skate Raja erinacea. Recently we cloned fragments of two AHR forms each from Greenland shark Somniosus microcephalus and sandbar shark Carcharhinus plumbeus. We are using rapid amplification of cDNA ends (RACE) to obtain the 5&’- and 3&’- ends of AHRs from all five species. The divergence and conservation of AHR genes in elasmobranchs will be discussed in the context of functional domains of the receptor. (Supported in part by NIH Grants ES06272 and ES05935). (Session 16, Sunday, July 8, Penn Stater, Room 207, 8:30)

Temporal and spatial variations in shark abundance and distribution in the estuary of the Ten Thousand Islands, Florida.

Sharks were collected at regular intervals from May through October 1999 and 2000 from three different habitats throughout the Ten Thousand Island Estuary. The habitats comprised gradients mainly defined by substrate, depth, salinity and temperature. The objectives of the present study were, 1) to determine the structure of shark communities; 2) to evaluate temporal trends in community structure; 3) to evaluate spatial trends in community structure and 4) to verify the physical factors responsible for the temporal and spatial patterns found. Spatial and temporal segregation of shark species was observed within the estuary during the wet season. Overall trends included an avoidance of the backwater area byCarcharhinus limbatus, whereas Carcharhinus leucas showed a preference for this habitat. These two species also differed in their temporal use of the estuary. C. limbatuswas most abundant from May through August and C. leucas from August through October.Sphyrna tiburo turned out to be an spatial-opportunist, most abundant from July through September. Correlation between intensity of shark use and salinity, temperature and depth was also observed. The study should help arguing about possible impacts of the planned change of the water run-off in this area on the local shark community. (Session 10, Saturday, July 7, Penn Stater, Room 207, 1:45)

Suction feeding in elasmobranchs: functional and evolutionary considerations 

Prey capture in elasmobranchs may involve ram, biting, filter feeding, compensatory suction, inertial suction or a combination of these behaviors. Morphological and physiological specializations for inertial suction feeding, as exemplified by the nurse sharkGinglymostoma cirratum, include a small terminal mouth with prominent labial cartilages that direct the gape anteriorly, small teeth, rapid mouth opening, and a modified kinematic prey capture sequence involving a fast opening phase that often lacks cranial elevation. Paleontological evidence suggests ancestral sharks were morphologically specialized for seizing and tearing their prey and primarily used ram prey capture. If this is correct, inertial suction feeding has repeatedly arisen within numerous elasmobranch lineages, often nested within groups of ram and compensatory suction feeding sharks. These inertial suction feeding elasmobranchs are predominantly benthic associated predators on smaller prey. We predict that inertial suction specialists will in general be shallow water dwellers that are weak or intermittent swimmers, be compressiform in shape, have more stereotyped kinematic and motor patterns of prey capture, and utilize ambushing and stalking of their smaller prey. Furthermore, inertial suction prey capture should predominate in the benthic associated batoids. A notable exception to this morphotype, the pulsatile suction-filter feeding whale shark Rhincodon typus, is discussed. (Session 29, Monday, July 9, Penn Stater, Room 105, 8:15)

Distribution and abundance of sharks in the Chesapeake Bight, U.S.A.

Scientific long-line survey data collected in the Chesapeake Bight from 1973-2000 were analyzed to describe the distribution and abundance of sharks. The most abundant species was Carcharhinus plumbeusbbsp;which migrates into the region in late Spring when water temperatures rise to 16-18C. Migration out of the region to south of Cape Hatteras usually occurs in late September or early October. Neonates and juveniles up to 4 or5 years of age use Chesapeake Bay as a nursery. Older juveniles occupy <10m depths along the coast but move further off shore (10-20m) as they get older. After pupping adult females move to depths>20m.Dusky sharks (C.obscurus exhibit the same seasonal migratory patterns, but utilize nearshore (<10m) areas for pupping.Blacktip (C.limbatus), spinner (C.brevipinna) and sharpnose (Rhizoprionodon terraenovae) sharks usually immigrate in June and seem to prefer higher temperatures (>22C) than the previous two species.Other species of importance are tiger (Galeocerdo cuveri), sand tiger (Carcharias taurus) sharks, and the grey smoothound (Mustelus canis). Seasonality and depth and temperature distributions are described for all species as well as size and sexual segregation. Another community of sharks occupys the outer continental shelf (>100m) in summer. Sharks taken there include bignose (C. altimus), mako (Isurus oxyrinchus) and blue (Prionace glauca). (Session 10, Saturday, July 7, Penn Stater, Room 207, 1:30)

Barrier island restoration and beach renourishment in coastal Louisiana: altering essential fish habitat

Annual land loss in coastal Louisiana is between 20-35 square miles/year and accounts for up to 80% of the national coastal loss. In response to this rapid land loss, Federal and state programs have been instigated to rebuild and restore Louisiana&’s coastal wetlands and barrier islands. Restoration projects have at times focused on restoring the physical environment without in-depth analysis of the ecological function of the habitat. Biological considerations, such as possible loss of valuable habitat for organisms using these areas, as well as the evaluation of restoration efforts for aquatic organisms, need to be more carefully considered. We discuss possible consequences of habitat alternation due to restoration projects, utilizing shark nursery habitat as an example. Research findings suggest that the Gulf of Mexico side of East Timbalier Island may function as a shark nursery, as may all Louisiana barrier islands. We have observed neonates, young-of-the-year, juveniles and/or adults for six species of sharks on the front island platform. Several shark species utilize the shallow surf zone, another potentially important habitat for sharks. We discuss possible effects of restoration/renourishment projects as they relate to these essential shark habitats. (Session 16, Sunday, July 8, Penn Stater, Room 207, 9:30)

Forces of Nature: Sharks in Eighteenth and Nineteenth Century European and American Art 

The purpose of this talk is to examine the manner in which sharks are portrayed in eighteenth and nineteenth century Western art in the context of changing attitudes concerning the relationship between humanity, religion and nature. Between 1700 and 1900 Western views of nature and the relationship of human experience to nature experienced radical change. The European colonial experience was driven by a perception of nature as a force to be dominated by humans, who were seen as being at the earthly pinnacle of thescala naturae. In this context, nature was viewed as hostile and implacable, to be constantly striven with and overcome. By the mid-to-late nineteenth century, changes in Western scientific and philosophical outlooks resulted in changing attitudes about the relationship between humanity and nature. In this latter view, humanity was seen more as an integral part of nature and in harmony with its forces. We will demonstrate that these changes in attitude are reflected in various paintings from this period that depict sharks representing forces of nature, including John Singleton Copley’s Watson and the Shark, J.M.W. Turner’s The Slave Ship and Winslow Homer’s The Gulf Stream. (Session 26, Monday, July 9, Penn Stater, Room 207, 11:00)

Calcitonin: potential roles in the bonnethead shark, Sphyrna tiburo 

Calcitonin is a phylogenetically ancient hormone that is produced in the parafollicular C cells of the thyroid gland in mammals and the ultimobranchial gland in all other jawed vertebrates. This hormone has been historically believed to be a major factor in calcium regulation. However, recent studies indicate that perhaps its primary role is in reproduction and/or development. The current study presents data on calcitonin bioactivity during the female reproductive cycle and embryonic development of the bonnethead shark, Sphyrna tiburo. Serum calcitonin concentrations within the mature female bonnethead shark over the reproductive cycle were determined using an enzyme-linked immunosorbent assay (ELISA) for salmon calcitonin. The presence of calcitonin in the reproductive tissues of the mature female bonnethead shark and within the developing embryo was demonstrated via immunohistochemical techniques. Results from ELISA demonstrate an elevation in serum calcitonin levels during the later stages of the reproductive cycle. Calcitonin bioactivity within the uterine tissue is present during the later stages of reproduction, paralleling the changes in serum calcitonin concentration and indicating a possible role in matrotrophy. Calcitonin bioactivity within the developing embryo demonstrates a possible role in the gastrointestinal tract and the pancreas. (Session 20, Sunday, July 8, Penn Stater, Room 207, 2:45)

The Influence of Tidal Stage and Lunar Phase on the Frequency of Shark Attacks 

Worldwide Sharks present a potential danger to swimmers entering the ocean. Past studies trying to rationalize and prevent shark attacks have focused on single, isolated parameters such as water temperature, water depth, water turbidity, and activities of the victim. They have not yet looked into the ecology of the environment in which the attacks occurred. This study addresses the ecological basis behind shark attacks. Tides have a large effect on the coastal environment, influencing the daily activities of many organisms, including sharks. If tides influence the behavior of sharks, attack frequencies will increase when the tides put them in closer proximity to humans. The tides are influenced by the moon, which is also said to play a major role in the activity patterns of animals. Therefore, attack frequency will increase during the phases of the lunar cycle that intensify the feeding behavior of sharks. The International Shark Attack File (ISAF) provided attack records for the analysis. Data from each case (date, time, and location) were used to find the tidal stage during the attack. An analysis of the patterns shown in histograms depicted the degree to which shark attacks are influenced by tidal stage and lunar phase. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Growth inhibition of mammalian tumor cell lines by conditioned media from in vitrocultures of immune cells from the epigonal organs of bonnethead sharks Sphyrna tiburo

Cell culture supernatants (conditioned media, CM) from 2-4 day serum-free cultures of unstimulated immune cells from epigonal organs of bonnethead sharks Sphyrna tiburodemonstrate a consistently high inhibitory activity against two mammalian tumor cell lines sensitive to different immune regulatory factors. At initial concentrations of 5×10⁴cells/mL, A375.S2 human malignant melanoma (interleukin-1 sensitive) and WEHI 164 murine fibrosarcoma (tumor necrosis factor sensitive) cells were co-cultured with various dilutions of bonnethead epigonal CM. Percent growth inhibition (%GI) was assessed after 96 h of culture by comparing the conversion of MTT to purple formazan by live cells in experimental and control cultures. Equal volume co-culture of CM (total protein – SEM, 9.16 – 0.63 mg/mL, n=21) with A375.S2 cells resulted in a mean %GI – SEM of 84.8 – 1.1, while co-culture of CM (total protein – SEM, 9.45 – 0.65 mg/mL, n=19) with WEHI 164 cells resulted in a mean %GI – SEM of 93.6 – 0.4. Preliminary characterization of bonnethead epigonal CM using SDS polyacrylamide gel electrophoresis indicates three major protein bands, one of which is consistent with the approximate molecular weight reported for both interleukin-1 and tumor necrosis factor from mammalian species. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Wild mating of the nurse sharks Ginglymostoma cirratum: Courtship behaviors, possible cooperation, and mechanisms of mate choice in an elasmobranch.

Elasmobranch copulation is often preceded by courtship activity. Ongoing life history studies of nurse sharks in the Dry Tortugas, FL have provided an opportunity for repeatable observations of shark courtship and mating behaviors. Ten reproductive behaviors are examined: refuge (23 occurrences), follow (4), shoal (6), grasp (11), avoidance (58), wait (10), carry (18), male competition (3), male cooperation (blocking) (3), and insertion and copulation (32). These behaviors are defined and documented, and clarified with video records that supplement past observations by the authors and others, and provide information about the timing and dynamics of nurse shark reproductive behaviors. (Session 7, Saturday, July 7, Penn Stater, Room 207, 9:45)

Ontogenic Development of Teeth in Embryos of Lamna nasus

The dental ontogeny in 21 embryos (7 male/14 female), ranging in size from 215-670 mm FL, was examined to trace the development of teeth in various tooth positions, to determine the variation in tooth form and to determine the polarity of tooth characters.In embryonic dentitions from individuals 413 mm FL or less, the teeth have a morphology very similar to those of some of the earliest chondrichthyans in the fossil record. Some of these smaller dentitions possessed upper and lower parasymphyseal teeth. In larger embryos, the dentition changes abruptly to a lamniform type resembling an that of an Odontaspis, but lacking lateral denticles; the first upper anterior tooth is also absent in all dentitions. These dentitions provide important information about the wide range of dental variation and provide information about which dental characters represent primitive or derived states. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Shark dive tourism: blessing or menace?

Shark dive tourism has increased dramatically in the last years and turned into a major income source for dive operations around the world. Along with this increasing popularity, questionable and unsafe habits have and led to heated debates over the meaning and dangerousness of this type of diving. A major source of problem is the cowboy mentality of many operations left unguided and not been backed up by scientific leadership. Shark diving has, if properly handled, a great potential in demystifying the wrongful image of sharks, and is a very important tool of applied conservation if mixed with correct information. However it is inevitable that this increasing boom must be guided and restricted by governmental agencies and other bodies to establish proper leadership, minimize risks of accidents, and maximize education. This paper focuses on the pros and cons of shark diving, its present problems caused by unqualified input, and currently established operations running a strictly scientific oriented dive operation. (Session 16, Sunday, July 8, Penn Stater, Room 207, 10:45)

Exploratory behavior: a typical cause for accidents with white sharks,Carcharodon carcharias

Shark accidents have wrongfully been categorized by authorities and inductive generalizations, forming an erroneous picture of contact approaches by sharks. Shark accidents are multi-layered with much more potential causes than initially assumed. One of the initial reasons why some shark species bite humans is exploratory behavior. A lot of media attention is given to white shark (Carcharodon carcharias) interactions with surfers and spearfishermen. It is inevitable that shark accidents be analyzed from a deductive point of view, excluding anthropomorphism and approaches of pure theoretical nature. The goal of shark accident analysis is not the description of the outcome of an interaction the accident – but the reasons behind it that eventually led to such an accident. This papers uses the analysis of the first ever filmed white shark accident on a diver and compares it with 10 randomly chosen white shark incidents on file where comparable injuries were found. (Session 7, Saturday, July 7, Penn Stater, Room 207, 8:00)

Australia Human induced approach behaviour on the bull shark (Carcharhinus leucas)

Approach behaviours of sharks leading to attacks on humans have been categorized in earlier years from a mostly theoretical point of view. However different shark species possess different approach behaviours due to size, sex, environment, situational circumstances and others. It is inevitable to study species individually exposing them to standardized scenarios and examine them on a intra and interspecies level. One of the major species being involved in incidents with humans is the bull shark (Carcharhinus leucas). An overview of general approach behaviour and interpretation of this species during different scenarios is given. (Session 3, Friday, July 6, Penn Stater, Room 207, 3:45)

Diet of young lemon sharks (Negaprion brevirostris) at an isolated seamount, Atol das Rocas, Brazil.

The diet of young lemon sharks was studied in Atol das Rocas, 144 nautical miles off Natal, Brazil, based on a non-destructive, stomach eversion, sampling technique. Sharks were captured with gillnets and dipnets in an embayment of the atoll’s lagoon, and subsequently anesthetized with tricaine. Stomach contents obtained through gastric eversion were preserved in isopropanol for qualitative and quantitative analyses. Eighteen sharks, total lenghts between 64.0 and 69.2 cm were sampled in March 2000. The stomachs of eight individuals were empty. One had a stomach so full that it precluded eversion. All the other nine sharks had teleost fishes in their stomachs (Albula sp., Ichthyapus sp., Synodus sp. and Sphyraena sp., as well as unidentified scales and vertebrae). Four of the sharks had cephalopod remains in their stomachs, including a possibly undescribed species of octopus. Further sampling to be conducted through the year 2001 will provide additional data on the diet of the species and on its role as an apex predator in atoll’s ecosystem. (Session 17, Sunday, July 8, Penn Stater, Room 206, 8:00)

The peculiar cestode fauna of alopiid sharks

Alopias pelagicus and A. superciliosus are parasitized by species of Litobothrium, a morphologically unique genus of tapeworms found exclusively in selected lamniform shark species. These shark species are also host to tapeworms of the genera Marsupiobothriumand Paraorygmatobothrium. In addition, a cestode of unknown taxonomic affinity has been collected from A. pelagicus. The cestode fauna of A. vulpinus differs from the former two species. Litobothrium is absent from A. vulpinus, and immature specimens of cestode genera commonly parasitic in lamnid sharks and carcharhinid sharks have been collected from Alopias vulpinus. Paraorygmatobothrium exiguum has been found in A. vulpinusfrom the Atlantic and Pacific oceans. A species each from the genera Pithophorus andParaorygmatobothrium have also been described from A. vulpinus, collected from the Pacific ocean. Molecular phylogenetic analyses of the cestode genera Litobothrium,Marsupiobothrium, Paraorygmatobothrium, the unknown cestode, and a number of other elasmobranch tapeworm species indicate the following: 1. the ªnative cestode fauna of alopiid sharks may be relictual in nature, and 2. other species clearly have been borrowed several times from a cestode clade evolutionarily linked to carharhiniform sharks. (Session 10, Saturday, July 7, Penn Stater, Room 207, 2:45)

The excavation kinematics and feeding-ventilatory coupling of the Atlantic cownose ray, Rhinoptera bonasus.

This study explores the feeding behavior and mechanics of a myliobatid, the Atlantic cownose ray Rhinoptera bonasus. High-speed videography was used to determine the prey excavation and capture kinematics of Rhinoptera bonasus. Videography and dye extraction were used to determine feeding behavior and water flow patterns during prey capture in the lab and in situ. Prey excavation involves repeated jaw opening and closing movements resulting in fluidization of the sand to uncover the benthic prey. Inertial suction prey capture during the preparatory phase is characterized by depression of the subrostral lobes and a slight closure of the jaws. The expansive phase begins with the closure ofthe spiracle, followed by depression of the mandible and protrusion of the palatoquadrate and nasal cartilages. During the compressive phase, the mandible is elevated toward the palatoquadrate and nasal cartilages grasping the prey. In the recovery phase, the jaws are brought back to a resting position and the spiracle is reopened. Thus, the feeding and ventilatory movements are coupled in time such that the ray only brings in water through the mouth during food capture. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

Genetic Structure Analysis of the Shortfin Mako (Isurus oxyrinchus) from Multiple Microsatellite Loci.

We investigated genetic population structure in the shortfin mako shark using multiple microsatellite markers. A previous study, which utilized restriction fragment length polymorphism of mitochondrial DNA, found significant structure. We developed several microsatellite loci by screening a sub-genomic library for di-, tri-, and tetra-nucleotide repeats. Positive clones were sequenced and primers for the polymerase chain reaction were designed. Primers that amplified polymorphic loci were used to genotype samples from four oceans (N. Atlantic, S. Atlantic, N. Pacific, and S. Pacific) via polyacrylamide gel electrophoresis. Analyses of Molecular Variance (AMOVA) results show lower levels of genetic divergence than expected. Primers developed were tested for possible cross-species amplification in several other species of sharks. The markers may be useful for studies in species including white sharks (Carcharodon carcharias), thresher sharks (Alopias spp.) and porbeagle (Lamna nasus). (Session 3, Friday, July 6, Penn Stater, Room 207, 4:15

Images of rays and sharks in seventeenth-century European art

From the 1570s to the close of the seventeenth century, artists in Italy and the Low Countries produced a substantial number of still life paintings representing the bounties of the ocean. Whether within the context of fish-stalls at local markets, kitchen interiors, or heaping piles of specimens carefully arranged on shore, the demand for and profusion of these images in early modern Europe raises a host of cultural and anthropological questions. Marine paintings in which rays and, less frequently, sharks figure prominently have been interpreted as lavish displays of abundance and wealth. Working from Neapolitan, Dutch and Flemish examples, this paper sheds light on the significance of sea animals as commodities in seventeenth-century economies. Perhaps more revealingly, my study examines images of these creatures as emblems of abundance in the context of European seaport and fishing centers where they functioned as important elements of the cult of the sea. (Session 26, Monday, July 9, Penn Stater, Room 207, 10:30)

Status of the Atlantic sharpnose shark (Rhizoprionodon terraenovae) US waters: results of preliminary analysis using an age-structured model.

Landings of small coastal sharks, and especially the Atlantic sharpnose shark

(Rhizoprionodon terraenovae), have increased in US waters as populations of large coastal species have declined. We are assessing the impact of fishing on R. terraenovaeusing an age-structured population model. A Bayesian approach to the assessment is used to incorporate both prior information about this and other species, and uncertainty about the data and population processes. Rhizoprionodon terraenovae is caught in a wide variety of fisheries, including the shark longline fishery, drift gillnet fishery, menhaden purse-seine fishery, shrimp trawl fishery, coastal gillnet fisheries, recreational fisheries, head boat fisheries, and many others. This diversity of fisheries makes the assessment more difficult. Data on the biology, gear selectivity, landing and discard practices, and population structure are included in the model. We present the preliminary results from the assessment for R. terraenovae. Difficulties with the assessment are discussed, and avenues for future research to improve the assessment are identified. (Session 3, Friday, July 6, Penn Stater, Room 207, 2:00)

Habitat issues in the conservation of smalltooth sawfish (Pristis pectinata)

Smalltooth sawfish (Pristis pectinata) are critically endangered in the western Atlantic, and are currently being considered for inclusion on the US Endangered Species List. Recovery of the sawfish population will depend upon reducing fishing mortality and providing sufficient suitable habitat. Information on the current distribution of P. pectinata was gathered from the public and research surveys. The results of this study have identified several human-mediated habitat issues in the conservation of sawfish. These include the use of canal developments as alternative habitat, and the use of power station outflows as thermal refuges during winter. The importance of these issues is discussed and future research directions suggested to further understand their impact. (Session 16, Sunday, July 8, Penn Stater, Room 207, 9:45)

Sharks under Arctic ice: acoustic tracking of Greenland sharks, Somniosus microcephalus

In May 1999, six Greenland sharks (Somniosus microcephalus) were tracked off northern Baffin Island, Nunavut, Canada to determine if vertical and horizontal movements were indicative of seal hunting behavior. Six Greenland sharks in the size range of 190-355 cm fork length were caught on lines baited with seal meat, then tagged with depth sensitive individually coded ultrasonic transmitters and tracked for 5.5-31.4 h. Horizontal and vertical movements were determined from data collected by manual tracking with a directional hydrophone and by five remote receivers set in a listening array. Horizontal rates of movement were found to differ significantly (p< 0.01) among sharks and ranged from 0.015 to 0.463 m s – 1, with a mean of 0.217 m s – 1. Rates of descent for the six tracked sharks were significantly (p<0.01) higher than rates of ascent. The sharks exhibited no apparent depth or temperature preference and during 31%, 26%, and 42% of the total aggregate tracking time, they were 0-70 m, 70-170 m, and 170-280 m deep, respectively. Pooled data for the six sharks indicated nocturnal movement into shallower depths. This study demonstrated that Greenland sharks are not exclusively benthic sharks and may actively hunt ringed seals just under landfast sea ice. (Session 10, Saturday, July 7, Penn Stater, Room 207, 11:00)

The physiological effects of angling on post-release survivorship in juvenile sandbar sharks (Carcharhinus plumbeus).

A post release survivorship study of juvenile sandbar sharks (Carcharhinus plumbeus) was conducted in Delaware Bay during 1999-2000. A total of 104 sharks were captured and sampled for changes in blood chemistry after exposure to exhaustive exercise. Of these, 24 sharks were angled in the field, sampled, tagged, and released. The remaining 80 sharks were transported to a holding tank, allowed to recover, and half were angled to exhaustion. To quantify recovery, these fish were sampled at 0,1.5, 3, 6, 10, 14 and 24 hours, then tagged and released. Blood was obtained by caudal venipuncture and analyzed immediately for blood gasses and glucose. Serum samples were sent to a commercial laboratory for the determination of blood metabolites, proteins, and electrolytes. Blood levels of lactate, PCO[-2], glucose, potassium, Ca, Mg, and CK were elevated during stress, while pH and HCO[-3,+-] levels declined. Most metabolites returned to normal within 6-10 hours. Moreover, 5 sharks were recaptured 0.03-12 months after release over the course of the study. These preliminary data indicate that sandbar sharks are able to physiologically recover after the exhaustive exercise associated with rod and reel angling and therefore, catch and release fishing may not severely impact neonatal and juvenile sandbar sharks in important nursery areas. (Session 20, Sunday, July 8, Penn Stater, Room 207, 11:30)

The activity pattern of the two carcharhinid shark species bull shark,Carcharhinus leucas and blacktip shark, Carcharhinus limbatus, in the estuary of the Ten Thousand Islands, Florida

Ultrasonic telemetry was used to determine the movement pattern of juvenile bull sharksCarcharhinus leucas and blacktip sharks, Carcharhinus limbatus in the estuary of the Ten Thousand Islands. A total of 11 bull sharks and 17 blacktip sharks were tracked between 4 and 23 hours. The sharks were tracked manually using a small boat with a trawling engine. The study was conducted during May through October 1999 and 2000. All bull sharks except one remained within 2000 meters of the capture cite and they never left the estuary while tracking. Bull sharks movement patterns did not appear to be effected by the tide. Blacktip sharks left the area with the outgoing tide to then return on almost the same path with the incoming tide. Blacktip sharks swam as far as 7000 meters away from the capture site and up to 3000 meters away from the shoreline. Only one bull shark displayed no tendency towards a specific core area where all the others showed places with significantly higher occupation rates, especially during daytime. All except three blacktip sharks occupied core areas. There was no significant difference in the swimming speed of the two shark species. (Session 10, Saturday, July 7, Penn Stater, Room 207, 11:30)

Phylogeography and conservation genetics of an endangered marine fish, the barndoor skate, Dipturus laevis

Analyses of long-term research surveys on the continental shelf between the Grand Banks of Newfoundland and southern New England suggest that the barndoor skate is at risk of extinction. This flattened, bottom-dwelling fish, which can grow up to 5 feet long, was one of the more abundant fish in the Northwest Atlantic as recently as the 1950s. But since then, heavy fishing pressures reduced the numbers of barndoor skates so precipitously that it is now the subject of a petition for listing under the U. S. Endangered Species Act. To help in the development of a management strategy to preserve the barndoor skate, we undertook a survey that consisted of the genetic typing of individual barndoor skates using mitochondrial markers. The sites where these individuals were collected were selected such that they would span a large portion of the barndoor skates’ geographic range. Statistical analysis of the data generated by this survey provided estimates of genetic diversity, degree of population subdivision, effective population size, and evolutionary relationship among sampled populations. The implication of these statistical findings are discussed with respect to the future management of barndoor skate populations, particularly regarding maintenance of genetic variation, reintroduction strategies, site selection of marine preserves, and the setting of future conservation priorities. (Session 38, Tuesday, July 10, Penn Stater, Room 207, 2:30)

Why are cartilaginous fishes so big?

The largest fishes in the sea have cartilaginous skeletons. There are a number of hypotheses as to why this might be true, though none explain the diversity and number of very large cartilaginous fishes. There is a functional limitation on size that may be a general explanation for the skewed size distribution. As a fish grows, its weight and the negative buoyancy of its skeleton grows as the third power of length. At the same time the thrust and lift generated by the fins grow with the square of length. At some length, there will be insufficient lift to counter the sinking force of the skeleton. A cartilaginous skeleton weighs less than a bony skeleton of the same length, so this theoretical maximal size is larger for the cartilaginous fish. This may provide an explanation for why the eight largest fishes are cartilaginous and the two largest bony fishes have cartilaginous skeletons. We show that cartilaginous fishes do have lighter skeletons per unit length than do bony fishes and that the heaviest cartilaginous skeletons are from benthic fishes. (Session 29, Monday, July 9, Penn Stater, Room 105, 8:00)

The ontogeny of the hornshark chndrocranium and the evolution of trabecular cartilage. 

The skeleton of the chondrichthian fishes is composed of cartilage, some of which is calcified. The vertebrae are completely calcified, while the remainder of the skeleton has one or more thin layers of calcified blocks covering a core of uncalcified cartilage. In a clade of stingrays containing hard-prey specialists an internal network of calcified struts augments the surface calcification. This strut-reinforced tissue is called trabecular cartilage. Some sharks also eat hard prey. We examined a series of Heterodontus francisci with a high-resolution CT scanner for evidence of trabecular cartilage. The CT scans and dissection revealed no trace of trabeculae. The jaws are the mechanical antithesis of those of hard-prey crushing stingrays. Rays have a well-calcified symphysis and the jaws meet at a joint with a large uncalcified region. In contrast heterodontids have a loose, uncalcified, ligamentous symphysis and the jaw joint is a well-calcified hinge. Dissection of other shark taxa that are reported to eat hard prey, Sphyrna tiburo and Orectolobus ornatus, did not reveal any trabecular cartilage. Trabecular cartilage appears to be an evolutionary innovation, confined to the myliobatid stingrays that allows them to eat harder prey than other cartilaginous fishes. (Session P-14, Saturday, July 7, Penn Stater, Deans Hall)

The True Tale of How Paleozoic Sharks Came to Rule my Life and Art

I will be presenting an illustrated informal talk about how fish came to dominate my artwork since moving to Alaska 20 years ago and more specifically how Paleozoic Chondrichthyans have recently dominated my illustration work.

This work includes various museum installations I have worked on, Discovery Channel films, and magazine assignments. I have worked for the past year on a suite of new shark drawings that I will debut in my slide talk. The drawings have been produced for a book to be published early next year. For more information on my work look at www.trollart.com (Session 26, Monday, July 9, Penn Stater, Room 207, 11:30)

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Growth rates of bonnethead sharks, Sphyrna tiburo, from the west coast of Florida estimated from tag-recapture data.

The growth of bonnethead sharks off the west coast of Florida was investigated using tag-release-recapture methods. Juvenile and adult bonnetheads were tagged with external nylon-barbed tags and released along Florida’s Gulf coast beginning in November of 1991. Growth data were obtained from 113 tag recaptures, 70 of which were recaptured by Mote Marine Laboratory biologists. The time at liberty ranged from 1 to 2029 days while the measured growth increments ranged from -5.5 to 30.5 cm. A maximum likelihood approach was employed to analyze these growth increment data. In addition to von Bertalanffy parameters, this method allows for an estimation of measurement error, growth variability, and treats data outliers objectively. A bootstrapping method was utilized to estimate confidence limits of the parameters. When combining all usable samples from all and K were estimated at 104.3 (cm STL) and 0.28 year – 1, respectively. A ^{areas, L}inf subset of female-only recaptures from Tampa Bay produced comparable growth parameters ^(Linf^{= 105.4 and K= 0.28 year – 1)}. The results will be discussed and compared with published results from age-at-length data for bonnetheads inhabiting similar regions in Florida. (Session 10, Saturday, July 7, Penn Stater, Room 207, 3:00)

Production of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) by peripheral blood leukocytes from nurse sharks Ginglymostoma cirratum

Nitric oxide (NO) is a potent cytotoxic molecule that serves as an antipathogenic agent in cell-mediated immune responses of higher vertebrates. Its production in immune cells results from the enzymatic transformation of L-arginine to L-citrulline by the inducible isoform of nitric oxide synthase (iNOS). To establish whether elasmobranchs produce reactive nitrogen intermediates, NO production by nurse shark Ginglymostoma cirratumperipheral blood leukocytes (PBL) stimulated with bacterial lipopolysaccharide (LPS) was investigated. Nurse shark PBL (6.25×10⁵, 1.25×10⁶, and 2.5×10⁶ cells/mL) were cultured for 24 to 96 h following stimulation with 0, 2.5, 5, 10, or 25 ug/mL LPS, in both serum supplemented (fetal bovine serum, FBS, and nurse shark serum, NSS) and serum-free culture conditions. Production of NO was measured indirectly via nitrite detection using the Griess reaction. Maximal NO production was observed after 72 h using a PBL concentration of 2.5×10⁶ cells/mL cultured with 10% FBS and stimulated with 10 ug/mL LPS. When PBL were cultured with a specific inhibitor of iNOS, the arginine analog L-N⁶-(1-iminoethyl)lysine (L-NIL), production of NO was inhibited. Procedures to confirm the presence of iNOS, which rapidly degrades in cell lysates, are being developed for Western blot analysis. (Session 20, Sunday, July 8, Penn Stater, Room 207, 2:00)

Ancient Greece: Tall but deadly fish ‘tails’

The wine dark sea of Homer still conveys the majesty and power of the seemingly limitless water surrounding Greece. This paper explores Greek and Roman values with regard to deadly encounters at sea, and aggressive attacks inspired from predators such as sharks. This investigation identifies the poet Homer as invaluable, stimulating the arts of his time (eighth century B.C.) and inspiring monumental works 700 years later in Greece and monumental acclaim by the first century A.D. In particular, murals for estates in Rome in the first century B.C. involved seascapes of Homer’s Odyssey. This tale involved the arduous return home from ancient Troy, and sudden death in several places and at sea that wiley Odysseus barely escaped. Sea monsters include the Scylla who grew immeasurably in the arts by the first century A.D. to command the attention of the emperor Tiberius in an imperial estate with sea grotto at Sperlonga south of Rome. Rhodian artists used the Scylla as their signed centerpiece, and best conveyed the ferocity of the combined physical forms and aggression, while permitting the viewer, the emperor to live as dangerously as Odysseus. (Session 26, Monday, July 9, Penn Stater, Room 207, 8:30)

Acute radiation exposure in the clearnose skate, Raja eglanteria: A histological study of the thymus 

Clearnose skate hatchlings (25g) were exposed to 0-75 Gray (1Gray = 100 rads) of ionizing radiation (n=122). The skates were sacrificed 10, 14, 20, 30 and 40 days post-irradiation. Thymii were fixed in 10% neutral buffered formalin and processed for routine histology. Fifty 3 micron cross-sections of thymus were collected at 50 micron intervals. Five thymus sections at 500 micron intervals were digitized for area analysis. The averaged areas were expressed as a percent of the control and treatments compared with ANOVA. Beginning at 1.5 Gray there was a significant logarithmic decline in thymus area as a function of radiation dose that became asymptotic after 15 Gray. Histologically, the medulla was infiltrated with large cysts containing apoptotic thymocytes and eosinophils. There was a decrease in cellularity of the cortex evident after only 1.5 Gray. This decline continued until radiation levels reached 15 Gray, when only stromal connective tissue remained. Repopulation of the thymus began at day 30 after 9 Gray but was not yet complete after 40 days. In skates exposed to 13.5 and 18 Gray the thymus began to recover its cellularity on day 40. There was no significant increase in thymic area over the 40 day recovery period. (Session 20, Sunday, July 8, Penn Stater, Room 207, 2:15)